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let's start with disorders of
carbohydrate metabolism we can see
patients with problems in glucose
metabolism fructose metabolism and
galactose metabolism I've drawn here the
galactose differently than glucose
because the O H group goes off in a
different direction it's a cartoon but I
think it's effective glycogen stores
diseases are probably the most common
issue around glucose metabolism
essentially enzyme defects in glycogen
breakdown result in an inability to make
glucose after a short period of fasting
in the liver and the muscle so patients
can present with both hepatic disease
and muscle disease in other words
they're having a problem getting the
glucose out of their glycogen stores
with hepatic disease a short fast can
cause hypoglycemia it usually shows up
in the first six months of life as
children start to space out their feeds
typically a newborn baby is eating every
two hours the glycogen stores aren't
that important as they get older they
rely on their glycogen stores more
because they are going longer distances
between feeds these patients can present
with muscle weakness and they can
present with hepatic cirrhosis at times
the muscle disease is a progressive
muscle weakness and sometimes can
involve the heart as well and in some
varieties of glycogen storage diseases
the cardiomyopathy is the most important
thing any child with cardiomyopathy is
primarily going to present with fatigue
let's go through three really common
glycogen storage diseases
the first one is von Gierke disease and
I like to think about von Gierke as
primarily in the liver this is also
glycogen storage disease type one these
patients will present with a profound
and challenging hypoglycemia they will
have hepatomegaly from their liver
involvement they will develop
hyperlipidemia as
well because of their underlying problem
they may have growth failure but they
will not primarily have weakness most of
their disease is rated related to the
liver that's as opposed to pompes
disease pompes disease can be very
severe in childhood or it can develop
later but this is glycogen storage
disease type 2 and it's primarily
involving the heart they do not develop
hypoglycemia they still do get somehow a
pata Meg Li but it can either be very
severe with a inevitable death by the
age of 2 or it can be more benign
clearly a heart failure is the most
important heralding symptom of Pompey's
disease the last example would be
McArdle's and when I think of McArdle's
I think of muscle muscle McArdle's this
is glycogen storage disease type 5 it
really only has muscle involvement so
these patients develop the weakness but
not as much of the other symptoms they
may develop rino problems from myoglobin
breakdown and sludging in the kidney
causing renal damage so monitoring for
that is important let's switch to
another type of sugar which is
galactosemia remember that galactose is
metabolized through a pathway involving
two major enzymes galactose is turned
into galactose 1-phosphate through
galactic kinase galactose 1-phosphate
has the enzyme GALT which then turns it
into glucose 1-phosphate
and then we can metabolize the glucose
remember that lactose the sugar in milk
is a galactose plus a glucose stuck
together lactase breaks those apart and
then for the galactose we use this
pathway to metabolize it in patients
with galactosemia they have a defect in
one of these two enzymes galacto kinase
deficiency is very rare we almost never
see it those children typically have a
milder course but GALT deficiency is not
too uncommon and
we do see periodically patients with
gulp deficiency Gulf deficiency usually
presents once milk is introduced as you
can imagine milk is introduced
essentially right at birth so we screen
for galactosemia in the newborn screen
so that we can prohibit the child from
getting milk once they're born if they
have this problem we need to give them a
special formula that does not have
galactose in it patients where they are
not picked up will develop failure to
gain weight vomiting lethargy jaundice
hypoglycemia and this is key for your
exam cataracts exams love to mention
cataracts these children can also
develop renal failure
so obviously screening for this disease
is very important even if effectively
picked up on the newborn screen and a
rapid intervention is made these
children can still have problems over
time they can develop speech delay a
taxi a-- going Adil failure problems can
happen but their course is much better
if we can make a dietary intervention
early in life very rare but we can see
hereditary fructose intolerance at well
this generally presents once fruit is
introduced these children can't
metabolize fructose well they generally
would develop an increased pyruvate and
lactate which leads to a metabolic
acidosis these children can develop and
Donnell pain nausea vomiting they can
have a severe hypoglycemia as well which
ironically is not relieved by fruit
juice they can develop lethargy seizure
and diarrhea so these children really
need to avoid fructose in their diet
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